Clamping device for molding apparatus



June 30, 1959 F. HANSBERG 2,892,313

CLAMPING DEVICE FOR MOLDING APPARATUS Filed April 26. 1956 3 Sheets-Sheet 1 Am M N n-d firro R! K:

June 30, 1959 F. HANSBERG 2,892,313

CLAMPING DEVICE FOR MOLDING APPARATUS Filed April 26, 1956 s Sheets-Sheet 2 FIG. 2

IN VENTOB FRITZ Hfl/VJEEAG HMMW J1me 1959 F. H'ANSBERG ,892,313

CLAMPING DEVICE FOR HOLDING APPARATUS Filed April 26, 1956 3 Sheets-Sheet 3 United States Patent h 2,892,313 eLAMPmG DEVICE FOR MOLDING APPARATUS Fritz Hansberg, Modena, Italy Application April 26, 1956, Serial No. 580,820 Claims priority, application Germany May 1955 11 Claims. c1. 60-545) A This invention relates to clamping devices and, more particularly, to a device that serves to clamp a core-box or ,mold boxto a machine table and to secure the several patts o'f the box together during a rapid filling operation.

Various constructions of core-box clamping devices have been provided which normally are operated by compressed air. These devices consist, in general, of a cylinder clamped to the machine table that has a pneu mane piston displaceably disposed therein, the piston rod of which urges a clamping jaw mounted on its free end against the core-box that is to be held together and filled.

Since the compressed air is used not only as a control niedium for displacing the clamping jaw, but also as a pressure medium for obtaining the necessary high contact pressure, it is always possible with these pneumatic clamping devices that the core-box will open during the abrupt filling operation because of the inherent compressibility of the gaseous pressure medium. 'While this danger has been quite prevalent with the conventional c'ore blowers', it is particularly a problem in connection 35 with the recently developed core shooting 01' ramming machines which work with compact jets of :sand and cause a particularly high pressure rise in the core-box during the filling operation because of the impact-like method of operation. Attempts have already been made to reduce the risk of the core-box from opening during the filling operation by increasing the contact pressure. Hewever, a simple increase of pressure is .diificult .because of the fact that in foundaries and workshops there is normally only a-constalnt air pressure-supply available. Accordingly, pressure multipliers have been proposed :in which the compressed air .acts 01153. large surfaced pneumatic piston, which in turn acts 'on a small hydraulic piston for placing a limited amount of oil under pressure to =obtain a higher pressure ratio. In this .type of an arrangement, however, the increase of pressure on filling the mold is transmitted through the piston hack to,. the compressed air which is, of course, compressible. Thus, in order to prevent the pressure jaw from being able to yield when the pressure increases, the initial piston .pres- 55 sure must exceed the maximum expected pressure that can oc'cur during the filling-of the box. Even where this can be done, the variety of type and sizes of boxes .used makes suitableadaptationineach case somewhat difficult.

Anzobject of this invention, therefore, is toprovide a 60 clamping device for core 'and mold boxes andthe like that will overcome the aforementioned difficulties and which is simple in construction and efficient in operation. ,uAnother object of this invention is to provide a clarnping device of the type described which utilizes compressed air as a control medium and'apressure-oil :as a reaction medium through which the clamping forces are transmitted without reacting through the compressed air.

1 Still another object of this invent-ion 'is to 'providea clamping device in which the initial contact pressure 70 at the-clamping jaw :need only besufiicient to hold .the

bbxitogether, but which provides an -.unyielding abutment 2,892,313 Patented June 30, 1959 in reaction to the maximum pressure occurring during the impact-like filling operation.

A further object of this invention is to provide a clamp ing device in which the hydraulic control of the locking valve is automatically operated by the pressure medium disposed between the pneumatic piston and the clamping device according to the increase in its specific pressure when the clamping jaw is engaged with the core-box.

A still further object of this invention is to provide a control unit for core-box clamping devices that is enclosed in a separate interchangeable housing.

Still another object of this invention is to provide a clamping device that is compact in construction and which embodies an adjustable mounting variable in height so as to be adapted for use in connection with various sizes, of core and mold boxes.

All of the foregoing and still further objects and advantages of this invention will become apparent from a study of the following specification, taken in connection with the accompanying drawing, wherein:

V Fig. 1 is a longitudinal sectional view through a clamp ing device made in accordance with this invention.

Fig. 2 is an enlarged detail view of the locking valve assembly shown in Fig. 1, and

Fig. 3 is a transverse sectional view taken along line 33 of Fig. 1, enlarged, showing the details of the adjustable mounting.

Referring now in detail 'to the figures of the drawing, the housing 1 of the clamping device is mounted so as to be adjustable in height on vertical pillars or posts '2 of a base plate 3. The housing is divided :by means of a central partition wall 4, into two chambers 5, .6. Within the chamber 5 at the head end of the housing, facing the core-box (not illustrated), there is mounted a clamping jaw piston 7 which at its free end 7 projects outwardly from the housing and has the actual clamping jaw .8 secured thereto. A return spring 9 acts between :the outer extremity of the chamber 5 and the piston 7 so as to urge the piston inwardly against the partition wall 4 of the housing. The outer end of the other chamber 6 of the housing is enlarged and closed in an air-tight manner at its outer extremity by means of a .cover plate 10 that has a compressed air line connector 11 for -supply ing the controlling compressed air from a control valve (not illustrated). A double-sided, stepped, pneumatic piston 12 is mounted within the chamber 6 andforms annular chamber 13 in the enlarged portion of :the chamher 6. Chamber 13 is in communication with the at mosphere through a bore 14. Both, the clamping jaw piston 7 ;and the penumaticpiston 12 have recesses 15, 16, respectively, that are adapted to receive the oppositely-projecting ends of'a locking valve housing 17 whi c h is fitted in the partition wall 4 of the housing. Housing 17 houses the loading valve assembly generally designated by :60. A fluid-tightplug 18 is provided at the top of thehousing on each side of the partition wall 4for sealing associated ports that are used to fill the chambers 5, 6 with pressure oil.

As more clearly shown in Fig. 2 the locking valve housing 17 has a flange 19 on the pneumatic piston side of the partition Wall 4 and ,a threaded portion 20 on the clamping jaw side thereof that is adapted to receive .a similarly threaded annular nut 21 that can be securely locked thereon by means of a grub screw 22. VA gaskettype packing insert 23 is carried by the partitionwalltfil so as to provide a fluid-tight seal with the flange 19 ,off the housing 17. A partition wall '24 within the valve housing .17 divides the interior of the housing into arfi st Chamber 25 situated on the pressure jaw side .of the u n i;t and a second chamber 26 situated on the pneumatic piston side thereof, which chambers are in communication with each other by .means of a valve passage ,-2 7 extending through the center of the wall 24. The outer end of the second chamber 26 is closed in a fluid-tight manner by means of a screw cap 28, while the outer extremity of the first chamber 25 is open at its free end and carries an annular seating ring 30 that is held therein by a spring clip 29. A control piston 31 is disposed within the second chamber 26 for limited longitudinal movement therein. The outer extremity of the piston 31 has a recess 32 in which a spring 33 is carried with one end seated at the inner extremity of the recess and the other end bearing against the screw cap 28 so as to urge the control piston 31 towards the partition wall 24. The inner side of the piston 31 is provided with a centrally disposed piston rod 34 that is constructed in the form of a push rod which projects through the valve passage-way 27 in the partition wall 24, into engagement with a valve body 35 that is mounted in the first chamber 25. The piston rod 34, under the pressure of the control piston spring 33, abuts against valve body 35 and tends to move the valve body outwardly and out of engagement with the valve seat 46 that also projects outwardly from and somewhat surrounds the valve passageway 27. The outer end 36 has a recess 37 longitudinally disposed therein adapted to receive one end of a locking spring 38 that bears against the annular disc 30 at its other end. The locking spring 38 tends to displace the piston valve 35, 36 towards the partition wall 24 and to urge the gasket or packing material 39 carried by the head of the piston valve against its associated valve seat 46. The second or control piston chamber 26 communiv cates with the pneumatic piston chamber 6 of the housing 1 by means of a plurality of radial bores 43, while the first or piston valve chamber 25 communicates with the clamping jaw piston chamber of the housing 1 through a longitudinally disposed passage-way 40 and associated apertures 41, 42.

Referring now to Figure 3, the valve housing 1 is shown to be slidably carried by the vertical pillars or posts 2. These posts 2 are removably secured by means of lock nuts 48 to the base 3 of the device and are adapted to be slidably received within cylindrical openings 49, 50 of the housing. Certain of these openings 50 are enlarged to compensate for irregularities and have set screws 51 associated therewith. These screws are selectively engageable with recesses or detents 52 in the respective support posts 2 for removably locking the unit in any one of a number of vertical positions relative to the base. In order to facilitate the adjustment of the unit, a detent 52 may be provided for each particular type or size of core-box to be used. 7

In operating the clamping device, compressed air is admitted from a manually-operated control valve through the compressed air line connector 11 and into the compressed air chamber 44 at the outer extremity of the housing 1. The admission of the compressed air displaces the pneumatic piston 12 inwardly towards the left, as viewed in the drawing, the air in the annular chamber 13 being expelled outwardly through the bore 14. This movement of the pneumatic piston 12 acts on the oil in the chamber 6, thereby producing a pressure that is transmitted by the oil which passes through the radial bores 43 and the valve housing 17 and then into the second chamber 26 without, for the time being, acting on the control piston 31 which is held in its inward position by the control piston spring 33. The oil pressure is further transmitted from the chamber 26 through the valve passage 27, into the open-ended chamber 5 of the housing 1, where it acts on the clamping jaw piston 7 to displace same outwardly against the resistance of the return spring 9, until the clamping jaw 8 comes to bear against the core-box (not illustrated), and meets resistance as it presses the parts of the box together. Continued movement of the pneumatic piston 12 is met with resistance after the clamping jaw engages the corebox, which resistance is transmitted to the pressure oil and has the eifect of increasing the specific pressure of the oil in the chambers 5, 6 and the intervening passages.

With a sufiiciently high increase in pressure, the pres-- sure oil which is now flowing through the radial bores 43 into the chamber 26, displaces the control piston 31 outwardly against the pressure of the control piston spring 33. The movement of the piston 31 also carries the piston rod 34 in the same direction which permits the piston the first chamber 25 and through the passage-way'40 and equalizing bores 45 that are provided in the stem of the piston valve 36. Oil then flows into the recess 37 of the piston until the locking spring 38 which is weaker than the control piston spring 33, aided by the pressure oil, presses the sealing surface or gasket 39 of the piston valve 35, 36 against its associated valve seat 46 thus to close the valve passage-way 27.

With the engagement of the gasket 39 with the valve seat 46, which closes the valve passage-way 27, the pressure oil in the chamber 5 and hence in the clamping jaw piston 7, is hydraulically locked and the clamping device and the core-box are ready for the filling of the core box. The sudden increase in pressure that occurs on filling the mold and which tends to burst the halves of the core-box apart, reacts through the clamping jaw 8, and clamping jaw piston 7 on the pressure oil in the chamber 5 but cannot act further on the oil which is in the closed chamber 6 and remains under normal pressure. Because of the pressure rise in the chamber 5, the,

gasket 39 of the piston valve 35, 36 is urged even more tightly against the valve seat 46 and continues to seal or close the valve passage-way 27. The increased reaction pressure of the clamping jaw piston 7 on the pressure oil in the chamber 5, is taken up by the partition wall 4 of the housing and transmitted through the clamping jaw. housing 1 and the vertical posts 2 to the clamping base plate 3 and then to the machine table. Thus, as a resultof the incompressibility of the pressure oil in the chamber 5, the clamping device acts during the filling of the mold like a rigid, solid, unyielding abutment surface whereby a reaction on the compressed air in the compressed air chamber 44 is prevented.

After themold is filled, the temporary excess pressure in the core-box disappears and the excess pressure in the hydraulic chamber 5 is restored to the normal contact pressure so that the pressure in the two chambers 5, 6 rlS equalized. Upon venting the pneumatic chamber 44 by means of the manually-operated central control valve,v in order to release the clamping device, the pressure oil in the chamber 6 urges the pneumatic piston 12 outwardly again. The equalization of the air pressure in the annular chamber 13 is effected through the bore 14, into which compensating air can be introduced if necessary. The drop in pressure in the chamber 26 of the valve housing 17, acting through the radial bores 43, restores to the control valve spring 33 its original preponderance over the valve locking spring 38 so that the'piston rod 34 urges the gasket end 39 of the piston valve 35, 36 out of engagement with the valve seat 46, thus urging the piston valve 35, 36 back to its open position against the resistance of the weaker valve locking spring 38. Under the action of the return spring 9, the clamping jaw piston 7' acts against the oil to transmit it back through the has been restored to its initial position together with the clamping jaw piston 7, under the pressure of the return spring 9, simultaneously releases the core-box whereby the device is ready for the next operation.

While this invention has been described with particular reference to the specific form shown in the drawing, it is to 'be understood that such showing is for illustrative purposes only and is not to be construed as imparting limitations upon the invention, which is best defined by the claims appended hereto.

I claim:

1. A device for clamping core and mold boxes during the filling thereof, comprising, in combination, a main housing defining a chamber and including a pneumatic piston side and a clamping jaw side and having a valve passageway connecting said pneumatic piston side and said clamping jaw side, a pneumatic piston slidably supported within one end of said housing, an air inlet at said one end of said housing for supplying pressurized air to actuate said pneumatic piston, a clamping jaw 'slidably carried by the opposite end of said chamber,

pneumatic pressure responsive hydraulic means including a. pressurized hydraulic medium intermediate said pneumatic piston and said clamping jaw for actuating said clamping jaw in response to admission of air to said pneumatic piston from said air inlet, a hydraulic pressure responsive locking valve member connected between said pneumatic piston and said clamping jaw for locking said clamping jaw in a relatively fixed adjusted position relative to said housing in response to the continued admission of air to said pneumatic piston, said locking member in- ;cluding a control piston being displaceable between an open and a closed position relative to said passageway, control piston spring means urging said control piston into one longitudinal direction, means for admitting the pressurized hydraulic medium of said hydraulic means to said control piston to urge said control piston into an opposite direction against the action of said control piston spring means to close the valve member and to lock said clamping jaw in said relatively fixed adjusted position, said spring loaded control piston being mounted on said pneumatic piston side and having a piston rod projecting through said valve passageway, and a valve body disposed on said clamping jaw side for engagement by said piston rod, said valve body being urged into closing engagement with said valve passageway by said displacement of said spring loaded control piston.

2. A device as set forth in claim 1 wherein said valve body comprises a resilient seal, the housing wall portion defining said passage-way forming a valve seat engageable by said seal.

3. A device as set forth in claim 2, further comprising a locking spring urging said valve body towards said piston rod, said control piston spring being of greater strength than said locking spring.

4. A device as set forth in claim 3, wherein said valve body is in form of an independent piston valve, said looking spring urging said piston valve into engagement with the free end of said piston rod.

5. A device as set forth in claim 4, wherein said independent piston valve is of hollow construction.

6. A device as set forth in claim 4, wherein said locking valve comprises an interchangeable locking valve housing, said locking valve housing having a passage in communication with both ends of said housing of the device, said control piston controlling the flow of hydraulic fluid through said passage.

7. A device as set forth in claim 6, wherein said locking valve housing is sealed on the side in which said control piston is disposed and is open on the side in which the valve body is disposed, and comprising a partition wall dividing said housing into said respective control piston side and said valve body side, said partition wall defining said valve passage-way through which said piston rod projects.

8. A device as set forth in claim 7, wherein said housing of the device comprises a rigid partition wall and said locking valve housing is carried thereby.

9. A device as set forth in claim 8 wherein said looking valve housing comprises a flange for engaging one side of said partition wall and a threaded portion for receiving an annular nut for engaging the other side of said partition wall so as to engage said partition wall therebetween in a fluid-tight manner.

10. A device as set forth in claim 9, wherein said pneumatic piston comprises a recess for receiving a portion of said locking valve housing.

11. A device as set forth in claim 9, wherein said clamping jaw comprises a piston having a recess disposed therein, said clamping jaw piston recess being adapted to receive a portion of said locking valve housing.

References ited in the file of this patent UNITED STATES PATENTS 1,715,380 Onsrud June 4, 1929 2,258,466 Naylor Oct. 7, 1941 2,436,656 Marsilius Feb. 24, 1948 2,603,067 Nissim July 15, 1952 2,642,797 Peters June 23, 1953 2,678,072 Verderber May 11, 1954 2,765,624 Hoschle et al Oct. 9, 1956 2,827,766 Huftord Mar. 25, 1958 FOREIGN PATENTS 462,487 France Nov. 24, 1913 444,955 Great Britain Mar. 30, 1936 670,839 Great Britain Apr. 23, 1952 

